PD-1high Tumor-infiltrating CD8+ T Cells Served As A Favorable Prognostic Biomarker in Triple-negative Breast Cancer

PD-1 has served as a hallmark of both exhausted T cells and tumor-reactive T cells. PD-1high CD8+ T cells were infiltrated in breast cancer (BC) and remained relatively unexplored. This study is among the first to examine the nature and distribution characteristics of PD-1high CD8+ T cells in BC. Since triple-negative BC (TNBC) patients still have the worst prognosis in BC, the prognostic value of PD-1high CD8+ T cells in TNBC was also explored.Tumor-infiltrating CD8+ T cells with different PD-1 expression (PD-1negative, PD-1low, PD-1high) were sorted from patients with BC and sequenced for the gene expression. Levels of exhaustion and resident memory T cell (TRM)-associated molecules and post-stimulation levels of the cytokines TNF-a, IL2, and IFN-? were assessed by flow cytometry. T-cell receptor Va and Vß expansion was also assessed in the CD8+ subsets. Finally, association between PD-1high CD8+ T cell frequency and clinicopathological features and prognostic value of PD-1high CD8+ T cells in the TNBC patients were evaluated.